Hydrocracking process

ABSTRACT

A CATALYTIC HYDROCRACKING PROCESS FOR PRODUCING HIGH VISCOSITY INDEX LUBRICATING OILS BY CONTACTING A MIXTURE OF HEAVY HYDROCARBONS HAVING A NITROGEN CONTENT LESS THAN 3000 P.P.M.W. WITH A CATALYST IN THE PRESENCE OF HYDROGEN UNDER HYDROCRACKING CONDITIONS AND ADDING TO SAID MIXTURE OF HYDROCARBONS UP TO ABOUT 300 P.P.M.W OF AMMONIA OR A NITROGEN COMPOUND WHICH YIELDS AMMONIA UNDER THE CONDITIONS OF THE PROCESS.

United States Patent Office 3,794,580 Patented Feb. 26, 1974 3,794,580 HYDROCRACKING PROCESS Peter Ladeur, Amsterdam, Netherlands, assignor to Shell Oil Company, New York, N.Y.

No Drawing. Filed Feb. 26, 1973, Ser. No. 336,154 Claims priority, application Great Britain, Mar. 7, 1972, 10,522/72 Int. Cl. Cg 13/02, 37/10 US. Cl. 208-110 8 Claims ABSTMCT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The present invention relates to a process for the preparation of lubricating oil by catalytic hydrocracking of a mixture of heavy hydrocarbons.

The yield of lubricating oil with a given viscosity index (VI) which is obtained by catalytic hydrocracking of a mixture of heavy hydrocarbons strongly depends on the cracking activity of the catalyst and on the nitrogen and aromatics contents of the mixtures of heavy hydrocarbons. By carefully adjusting the cracking activity of the catalyst to the nitrogen and aromatics content of the feed, an optimum catalyst can be prepared which gives the maximum obtainable yield of the lubricating oil concerned if applied for hydrocracking said feed. If this optimum catalyst is, however, applied for hydrocracking said feed to prepare a lubricating oil with a VI above the VI level for which this catalyst has been designed, a rather disappointing yield of the lubricating oil with higher VI is obtained, compared with the maximum obtainable yield of this lubricating oil from said feed. The same holds, if the optimum catalyst is applied for the preparation of a lubricating oil having the aforementioned given VI, but starting from a mixture of heavy hydrocarbons having a nitrogen and/ or aromatics content below the level for which this catalyst has been designed. Again a rather disappointing yield of the lubricating oil with the given VI is obtained, compared with the maximum obtainable yield of this lubricating oil from the feed concerned.

Heretofore catalysts having different cracking activities had to be designed for the preparation of lubricating oils having different VIs by hydrocracking of the same feed as well as for the preparation of lubricating oils having the same VI by hydrocracking of feeds having a different nitrogen and/or aromatics content. It has now been found that these drawbacks of lubricating oil preparation by bydrocracking can be avoided by addition of a certain quantity of a nitrogen compound to the feed to be hydrocracked.

THE INVENTION An optimum catalyst for preparing a lubricating oil with a given VI by hydrocracking a mixture of heavy hydrocarbons can be applied for preparing high yields of lubracating oils having a higher VI from the same feed by adding a certain quantity of a nitrogen compound to the feed. The process is especially applicable for the preparation of high yields of lubricating oils having a VI greater than 100. In general it can be said that addition of a nitrogen compound to the feed olferswthe possibility of preparing with a single catalyst in high yield lubricating oils having different VIs from the same feed as well as lubricating oils having the same VI from feeds having a different nitrogen and aromatics content.

The quantity of nitrogen compound which should be added to the feed depends on the required VI level of the lubricating oil to be prepared and on the nitrogen and aromatics content of the mixture of heavy hydrocarbons which is applied as feed. The quantity of nitrogen compound added to the feed will be up to about 3000 p.p.m.w., with the quantity being larger as the required VI level is higher and as the nitrogen and aromatics contents of the feed is lower. The exact quantity of nitrogen which should be added in a certain case can easily be determined with the aid of a few scouting experiments in which different quantities of a nitrogen compound are added to the feed concerned.

Preferred nitrogen compounds which may be added to the feed in the process according to the invention are ammonia and nitrogen compounds which yield ammonia under the conditions of the process. Examples of suitable nitrogen compounds are ammonia, ammonium hydroxide, alkylamines such as mono-, diand trimethylamine and mono-, diand tri-ethylamine, alkanolamines such as mono-, diand tri-ethanolamine, arylamines such as mono-, diand tri-phenylamines, mixed alkylarylamines such as phenylethylamine, alkyldiamines such as ethylenediamine and aryldiamines such as phenylenediamine. Although only the lower-molecular-weight amines have been enumerated, the higher-molecular-weight members of the various homologous series may be used as well. In addition to the aforementioned compounds a large number of other nitrogen compounds may be used. Examples of these nitrogen-containing compounds are organic nitrates, nitrites, nitriles, nitroso compounds, amides, imides, ammonium salts (such as ammonium acetate), urea and derivatives thereof, cyanates, isocyanates, isocyanides, quaternary ammonium compounds, nitro compounds, pyridine and derivatives thereof such as quinoline and piperidines, oximes, hydroxylamine and azo compounds. At least part of the quantity of nitrogen which is added to the feed may originate from ammonia which has been isolated from the hydrocracked product and recycled to the hydrocracking reactor.

For the preparation of lubricating oils according to the present invention, preferably use is made of a catalyst comprising one or more metals of Groups VI-B, VII-B and/or VIII deposited on a support consisting of one or more oxides of Group II, III and/or IV elements. Examples of suitable metals are nickel, cobalt, molybdenum and tungsten. Preference is given to catalysts comprising at least one metal selected from the group consisting of nickel and cobalt and at least one metal selected from the group consisting of molybdenum and tungsten, inparticular catalysts comprising 0.0250.8 and more in particular ODS-0.7 gat nickel and/or cobalt and 0.050.5 and more in particular 0.1-0.4 gat molybdenum and/or tungsten per g. carrier. Moreover, the atomic ratio between nickel and/or cobalt on the one hand and molybdenum and/0r tungsten on the other hand is preferably in the range of from 0.1:1 to 2:1 and in particular in the range of from 0.211 to 1.6:1. The metals may be incorporated into the catalysts by any one of the techniques for the preparation of supported catalysts well-known in the art, e.g. by coimpregnation of a carrier in one or more steps with an aqueous solution comprising salts of the metals concerned, followed by drying and calcining. The metals may be present on the carrier either as such or as metal oxides or metal sulphides. The catalysts are preferably used in their sulphidic form. Sulphidation of the catalysts may be carried out by anyone of the techniques for sulphidation of catalysts well-known in the art, e.g. by contacting the catalyst with a mixture of hydrogen and hydrogen sulphide or with hydrogen and a sulphur-containing hydrocarbon oil, such as sulphur-containing gas oil.

Examples of suitable carriers for the catalysts to be applied according to the present invention are silica, alumina, zirconia and magnesia, as well as mixtures of these oxides, such as silica-alumina, silica-magnesia and silica-zirconia. Preference is given to catalysts comprising as carrier material alumina or silica-zirconia.

Catalysts employed according to the present invention may further comprise promoters such as fluorine, boron and phosphorus. Fluorine may be incorporated into the catalysts at any stage of the catalyst preparation. Fluorine may also be incorporated into the catalysts by in-situ fluoriding of the catalyst in an early stage (e.g. during or after start-up) of the hydrocracking process. In-situ fluoriding of the catalysts may be performed by adding a suitable fluorine compound to the gas and/ or liquid feed stream which is passed over the catalysts. The amount of fluorine present in the catalysts employed according to the invention is preferably 0.5 to 7 percent W.

For the preparation of lubricating oils according to the present invention, preferably one of the following types of catalysts is used.

A catalyst which has been prepared by impregnating a porous carrier with a solution comprising (a) one or more compounds of metals selected from the group consisting of nickel, cobalt, molybdenum and tungsten, (b) phosphate ions and (c) peroxide ions, followed by drying and calcining the composite.

A fluorine containing supported catalyst comprising at least one metal selected from the group consisting of nickel, cobalt, molybdenum and tungsten, into which catalyst at least part of the fluorine has been incorporated by fluoriding in-situ.

A catalyst which has been prepared by incorporating into an alumina hydrogel, which hydrogel on drying and calcination would give a xerogel having a compacted bulk density of 0.75 to 1.6 g./ml. and a pore volume of 0.15 to 0.5 ml./g., one or more compounds of metals selected from the group consisting of nickel, cobalt, molybdenum and tungsten, from an aqueous solution in sufiicient concentration to provide a content of these metals in the finished catalyst, expressed as the metal oxides, of 30 to 65 percent w., followed by drying and calcination of the composite.

A supported catalyst comprising one or more sulphides of metals selected from the group consisting of nickel, cobalt, molybdenum and tungsten which has been prepared by treating a composition comprising a porous carrier, one or more water-soluble salts of the abovementioned metals and water, with a hydrogen-sulphidecontaining gas at a temperature below 150 C. and subsequently heating up the material in a hydrogen-containing gas to a final temperature above 200 C.; the amount of water present in the composition to be treated with the hydrogen-sulphide-containing gas should correspond with the amount of water present in the composition after drying the same in a dry gas at 100 C. increased by 20 to 120% of the amount of water which said dried composition is capable of taking up within the pores of the carrier at 20 C.

As a mixture of heavy hydrocarbons which may serve as starting material for the preparation of lubricating oil according to the invention, preference is given to waxy lubricating oil fractions obtained in the distillation at reduced pressure of atmospheric distillation residues of waxy crude oils and waxes separated from these waxy lubricating oil fractions or from waxy lubricating oil fractions obtained by hydrocracking. Examples of such waxy lubricating oil fractions are spindle oil (SO), l gh machine oil (LMO) and medium hea y machine oil (MMO) waxy distillates and deasphalted oils, SO, LMO- and MMO waxy ratfinates and waxy bright stocks obtained from the above-mentioned lubricating oil fractions by treating them with a selective solvent for aromatics such as furfural, and SO, LMO, MMO-, DAO- and BS slack waxes obtained from the abovementioned lubricating oil fractions by dewaxing. Mixtures of one or more distillate lubricating oil fractions and/or one or more residual lubricating oil fractions and/ or one or more slack waxes may also be used as starting material for the preparation of lubricating oil according to the invention. Very attractive results can be obtained with the following mixtures of heavy hydrocarbons as starting materials: deasphalted residual petroleum fractions and raflinates prepared from these deasphalted petroleum petroleum fractions or from heavy cat cracker cycle oils by treating them with a selected solvent for aromatics such as furfural. Preferably, the nitrogen content of these heavy hydrocarbon fractions before addition of nitrogencontaining compounds amounts to less than 3000 p.p.m.w.

Hydrocracking of heavy hydrocarbon fractions for the production of lubricating oil according to the invention is carried out by contacting the heavy hydrocarbon fractions, after addition of the required quantity of nitrogen thereto, at elevated temperature and pressure and in the presence of hydrogen, with a suitable catalyst, which is preferably present in one or more beds of particles of a size between 0.5 and 3 mm.

Suitable hydrocracking conditions are: a temperature of from 350 to 450 C., a pressure of from 5 to 250 bar, a hydrogen/feed ratio of from to 5000 N 1 hydrogen per kg. feed and a space velocity of from 0.2 to 5.0 kg. feed per litre of catalyst per hour. It is preferred to apply the following conditions: a temperature of from 375 to 425 C., a pressure of from 100 to 200 bar, a hydrogen/ feed ratio of from 500 to 2500 N 1 hydrogen per kg. feed and a space velocity of from 0.5 to 1.5 per litre of catalyst per hour.

Lubricating oils prepared by the process of the invention have a low aromatics content. Lubricating oils with still lower aromatics content can be prepared by the process according to the invention if the hydrocracking step is followed by a hydrofinishing step. Hydrofinishing of the hydrocrackate may be effected by contacting the hydrocrackate, at elevated temperature and pressure and in the presence of hydrogen, with a hydrofinishing catalyst. The pressure, space velocity and gas rate which are applied in the hydrofinishing step may be selected within the same ranges as given above for the hydrocracking step. The hydrofinishing temperature is preferably selected between 225 and 400 C. and in particular between 275 and 375 C. The temperature adapted in the hydrofinishing step should be at least 25 C. below the temperature at which the hydrocracking step is effected. Suitable hydrofinishing catalysts are catalysts comprising one or more metals of Groups VIB, VII-B and/or VIII on a carrier.

The eflluent of the hydrocracking reactor, or, if hydrofinishing is applied, the efiiuent from the hydrofinishing reactor is cooled and separated into a hydrogen-rich gas and a liquid product. The liquid product contains hydrocarbons boiling below the boiling range of lubricating oil and hydrocarbons boiling within the said range. The hydrocarbons which boil below said range are separated from the higher-boiling residue, preferably by fractional distillation. The cutting point of this distillation is preferably selected such that the high-boiling residue has an initial boiling point in the range of from 350 to 550 C. In addition to excellent lubricating oil components, this residue generally contains n-paraffins which solidify at ambient temperature and consequently have an adverse effect on the pour point of the lubricating oil. In order to produce a suitable lubricating oil from the residue it is therefore preferred to dewax this residue. The dewaxing treatm nt may be carried out in any manner desired. De-

waxing is preferably effected by means of a mixture of methyl ethyl ketone and toluene at a temperature between and 40 C. and at a solvent-to-oil volume ratio of between 1:1 and 10: 1. To increase the yield of lubricating oil, it is preferred that at least part of the separated wax be recirculated to the hydrocracking reactor.

The invention will now further be elucidated by means of the following examples.

Eight catalyst (A-H) were applied in hydrocracking experiments for the preparation of lubricating oil from nine mixtures of heavy hydrocarbons (I-IX). The compositions of the catalysts and the feeds were as follows.

Catalyst A Ni/Mo/P/Al- O catalyst comprising 0.06 gat nickel, 0.15 gat molybdenum and 3.1 p.b.w. phosphorus per 100 p.h.w. alumina. This catalyst had been prepared by impregnating alumina with an aqueous solution comprising nickel nitrate, phosphoric acid, ammonium molybdate and hydrogen peroxide followed by drying and calcining the composite.

Catalyst B Ni/Mo/P/F/Al O catalyst containing 2.6 percent w. fluorine. This catalyst had been prepared by impregnation of catalyst A with an aqueous solution of ammonium fluoride followed by drying and calcining the composite.

Catalyst C Ni/Mo/P/F/Al o catalyst containing 4.6 percent w. fluorine. This catalyst had been prepared by in-Situ fluoriding of catalyst B.

Catalyst D Ni/W/F/Al O catalyst comprising 31.0 p.b.w. nickel and 58.0 p.b.w. tungsten per 100 p.b.w. alumina and 5.7% w. fluorine. This catalyst had been prepared by mixing an alumina hydrogel with an aqueous solution comprising nickel nitrate, ammonium tungstate and ammonium fluoride of which solution the pH had been adjusted to 6.5 with the aid of 25% ammonia. The mixture was heated at 80 C.; the gel was filtered, extruded, dried and calcined. The alumina applied for the preparation of this catalyst gave on drying and calcining a xerogel having compacted bulk density between 0.75 and 1.6 g./ml. and a pore volume between 0.15 and 0.5 ml./ g.

Catalyst E Ni/W/F/Al O' catalyst comprising 3.3 p.b.w. nickel and 25.4 p.b.w. tungsten per 100 p.b.w. alumina and 3.7 percent w. fluorine. This catalyst had been prepared by im pregnating alumina with an aqueous solution of am monium tungstate and nickel nitrate. After adjusting the degree of wetting to 100% the composition was first treated with H 8 at bar gauge and 75 C. for 16 hours, subsequently heated in a stream of H S-containing H (9 percent v. H 8, 10 bar gauge, 25,000 N. 1.1 .h to 400 C. within 2 hours and finally kept at 400 C. for about 2 hours in this gas stream. (The expression degree of wetting used hereinafter refers to the amount of water which is present in the composition in addition to the amount of water present therein after drying the composition in a dry gas at 110 C. The degree of wetting, is expressed as a percentage of the amount of water which said dried composition is capable of taking up in the pores of the carrier at C.). Fuorine had been introduced into the catalyst by in-situ fluoriding.

Catalyst F and G Ni/W/F/Al O catalysts comprising 6.6 p.b.w. nickel and 50.8 p.b.w. tungsten per 100 p.b.w. alumina and 1.1 and 3.1 percent w. fluorine, respectively. These catalysts had been prepared in the same way as catalyst E.

6 Catalyst H Ni/MofiP/F/Al O catalyst comprising 11.9 p.b.w. nickel, 20.1 p.b.w. molybdenum and 2.6 p.b.w. phosphorus per p.b.w. alumina and about 2 percent w. fluorine. Fluorine had been introduced into the catalyst by in-situ fluoriding.

In-situ fluoriding of catalysts C, E, F, G and H was carried out by addition of ortho-fluorotolueneto the feed during the initial stage of the hydrocracking process.

Feed I.Deasphalted distillation residue of a Middle East crude. Nitrogen content: 760 p.p.m.w.; aromatics content: 59 percent w.; VI after dewaxing at 30 C.: 78.

Feed II.Feed I after addition of 450 p.p.m. N as pyridine.

Feed III.Feed I after addition of 900 p.p.m.w. N as pyridine.

Feed IV.Raflinate obtained after extraction of Feed I with furfural. Nitrogen content: 320 p.p.m.w.; aromatic content: 47 percent w.; VI after dewaxing at 30 C.: 93.

Feed V.Feed IV after addition of 450 p.p.m.w. N as pyridine.

Feed VI.Feed IV after addition of 900 p.p.m.w. N as pyridine.

Feed VII.Raflinate obtained after extraction of a heavy cat. cracker cycle oil with furfural. Basic nitrogen content: 2 p.p.m.w.; aromatics content: 27.3 mmol/ 100 g.; 20 percent v. point in U.O.P distillation: 402 C.; VI after dewaxing at 27 C.: 117.

Feed VIII.-Feed VII after addition of 100 p.p.m.w. N as tri-n-butylarnine.

Feed IX.Feed VII after addition of 200 p.p.m.w. N as tri-n-butylamine.

The VIs given in the examplesof this patent application have been determined according to ASTM method D2270.

The hydrocracking experiments 1-6 were carried out under the following conditions:

Pressure 150 bar.

LHSV 1 l. 1- h.- Gas rate 2000 N 1. kg? Catalyst bed 100 ml. Catalyst size 0.5-1.4 mm.

The catalysts were used in the sulphided form. Sulphidation of catalysts A-D and H was carried out by contacting the catalysts with hydrogen and a sulphur-containing gas oil. Dewaxing was carried out with a 1:1 mixture of methylethyl ketone and toluene.

EXPERIMENT 1 Lubricating oils having a VI of and 140, respectively, after topping at 400 C. and dewaxing at 30 C., were prepared by hydrocracking feeds 1, IV, V and VI over catalyst B. The temperature requirements (temperatures which should be applied to obtain the lubricating oil?J 1concerned) and yields of dewaxed oils are given in Ta e I.

TAB LE I 130 V.I. lubricating oil Yield on feed, wt. percent V.I. lubricating oil Yield on feed, wt. percent Temp. requirement, C.

Temp. requirement, 0.

Feed Catalyst 7 cating oils with catalyst B. By addition of a nitrogen compound to Feed IV (Feed V=Feed IV+450 p.p.m.w. N and Feed VI=Feed IV+900 p.p.m.w. N) the yield of 130 and 140 VI lubricating oils from this feed with catalyst B is strongly increased.

EXPERIMENT 2 Lubricating oils having a VI of 130 and 140, respectively, after topping at 400 C. and dewaxing at 30 C., were prepared by hydrocracking Feed IV over catalyst A. The temperature requirements and yields of dewaxed oils are given in Table II. For comparison, the results of Experiment 1 in which Feed IV was hydrocracked over catalyst B, have been incorporated in the table.

TABLE II 130 V.I. lubricating oil 140 V.I. lubricating oil Temp. Yield on Temp. Yield on requirefeed, wt. requirefeed, wt. Feed Catalyst ment, C. percent ment, C. percent IV A 417 31 424 IV B 402 28 410 15 Table II demonstrates that improved yields of 130 and 140 VI lubricating oils can be realized by using an unfluorided catalyst (Catalyst B=Catalyst A+2.6% w. F). However, the improvement is not equal to that which can be realized by adding a nitrogen compound to the feed. Compared with catalyst B, catalyst A shows a higher yield of the lubricating oils concerned, but also a much higher temperature requirement.

EXPERIMENT 3 Lubricating oils having a VI of 110 after topping at 400 C. and dewaxing at 30 C., were prepared by hydrocracking of Feeds I and II over catalysts B and C. The temperature requirements and yields of dewaxed oils are given in Table III.

TABLE III 110 V.I. lubricating oil Temp. Yield on requirefeed, wt. Catalyst ment, 0. percent B 400 45 C 400 C 400 The figures given in Table III show that catalyst C is less suitable than catalyst B for the preparation of 110 VI lubricating oil from Feed 1. After addition of a nitrogen compound to Feed I (Feed II=Feed I+450 p.p.m.w. N), catalyst C shows the same excellent performance as catalyst B.

EXPERIMENT 4 Lubricating oils having a VI of 130 after topping at 400 C. and dewaxing at 30 C., were prepared by hydrocracking of Feeds I and III over catalysts F and G. The temperature requirements and yields of dewaxed oils are given in Table IV.

TABLE IV 110 VI. lubricating oil Temp. Yield on requireed, wt. Feed Catalyst merit, C. percent The figures given in Table IV show that catalyst G is less suitable than catalyst F for the preparation of 130 VI lubricating oil from Feed 1. After addition of a nitrogen compound to Feed I (Feed III=Feed I+900 p.p.m.w. N) catalyst G shows a performance which is comparable with that of catalyst F.

Catalysts F and G are both prepared from the same Ni/W/Al O catalyst by in-situ fluoriding and differ only in fluorine content (catalyst F: 1.1% w. F and catalyst G: 3.1% w. F). This experiment shows another attractive feature of the process according to the invention. If by some kind of misoperation during the in-situ fluoriding of the catalyst, too much fluorine has been incorporated therein, it is no longer necessary to replace the catalyst by one having a lower fluorine content, but it is suflicient to add a certain quantity of a nitrogen compound to the feed to be hydrocracked.

EXPERIMENT 5 Lubricating oils having a VI of 130 and 140, respectively, after topping at 400 C. and dewaxing at 30 C., were prepared by hydrocracking of Feeds I and II over catalysts B and E. The temperature requirements and yields of dewaxed oils are given in Table V.

TABLE V 130 V.I. lubricating oil 140 VI lubricating oil Temp. Yield on Temp. Yield on requireteed, wt. requirefeed, Wt. Feed Catalyst ment, C. percent ment, 0. percent I B 416 32 424 21 E 416 36 424 20 E 426 26 The figures given in Table V show that catalyst E is more suitable than catalyst B for the preparation of 130 VI lubricating oil from Feed I, but that catalyst E is less suitable than catalyst B for the preparation of 140 VI lubricating oil from that feed. By addition of a nitrogen compound to Feed I (Feed II=Feed I+450 p.p.m.w. N) the yield of 140 VI lubricating oil from this feed with catalyst E is strongly increased.

EXPERIMENT 6 Lubricating oils having a VI of 140 after topping at 400 C. and dewaxing at 30 C., were prepared by hydrocracking of Feeds I and III over catalyst D. The temperature requirements and yields of dewaxed oil are given in Table VI.

TABLE VI V1. lubricating oil Temp. Yield on requireteed, wt. Feed Catalyst ment, 0. percent I D 415 24 III D 417 30 The figures given in Table VI show that the yield of 140 VI lubricating oil from Feed I with catalyst D is strongly increased by addition of a nitrogen compound to said feed (Feed III=Feed I+900 p.p.m.w. N).

EXPERIMENT 7 Lubricating oils having a VI of after topping at 400 C. and dewaxing at 27 C., were prepared by hydrocracking of Feeds VII, VIII and IX over catalyst H. This hydrocracking experiment was carried out under the following conditions:

The figures given in Table VII show that the yield of 130 VI lubricating oil from Feed VII with catalyst H is strongly increased by addition of a nitrogen compound to said feed (Feed VIII=Feed VII+100 p.p.m.w. N and Feed IX=Feed VII+200 p.p.m.w. N).

What is claimed is:

1. A hydrocracking process for preparing lubricating oils having a viscosity index greater than 100 which comprises contacting a mixture of heavy hydrocarbons having a nitrogen content less than 3000 p.p.m.w. with a catalyst comprising at least one metal selected from the group consisting of nickel and cobalt and at least one metal selected from the group consisting of molybdenum and tungsten composited with a support selected from the group consisting of alumina and silica-zirconia, in the presence of hydrogen under hydrocracking conditions; and adding to said mixture of heavy hydrocarbons up to about 3000 p.p.m.w. of ammonia or a nitrogen compound which yields ammonia under the conditions of the process.

2. The process of claim 1 wherein the catalyst comprises 0.025-0.8 gram atom nickel and/or cobalt and 0.'05-0.5 gram atom molybdenum and/or tungsten per 100 grams carrier.

3. The process of claim 2 wherein the atomic ratio in the catalyst between nickel and/r cobalt on the one hand and molybdenum and/or tungsten on the other hand is in the range of from 0.111 to 2: 1.

4. The process of claim 1 wherein the catalyst is applied in its sulphidic form.

5. The process of claim 1 wherein the catalyst comprises from 0.5 to 7% w. flourine.

6. The process of claim 1 wherein the mixture of heavy hydrocarbons is a deasphalted residual petrolum fraction.

7. The process of claim 1 wherein the mixture of heavy hydrocarbons is a raifinate Which has been prepared from a deasphalted residual petroleum fraction or from a heavy cat. cracker cycle oil by treating with a selective solvent for aromatics removal.

8. The process of claim 1 wherein hydrocracking is carried out at a temperature of from 350 to 450 C., a pressure of from 5 to 250 bar, a hydrogen/feed ratio of from to 5000 N 1 hydrogen per kg. feed and a space velocity of from 0.2 to 5.0 kg. per liter catalyst per hour.

References Cited UNITED STATES PATENTS 3,278,417 10/ 1966 Van Driesen 208-108 3,284,340 11/1966 Halik et a1 2081 11 3,285,848 11/1966 Donaldson et al. 2081l0 3,644,200 2/1972 Young 208-120 3,684,695 8/1972 Neel et a1. 208--110 3,706,658 12/ 1972 Hass et a1. 208111 DELBERT E. GANTZ, Primary Examiner G. E. SCHMITKONS, Assistant Examiner US. Cl. X.R. 

